Polarimetric apparatus



Feb. 3- 1925- 1,525,145

P, R. 0R12 POLARIMETRIC APPARATUS Fled May 12, 1923 INVENTOR:

By his A 1 s,

P. R. ORD,

Patented Feb. v3, 1925".

UNITED STATES PA'rEnr omer..

'BERCY ROBERT ORD, OF LONDON, ENGLAND, ASSIGNOR '.lO ADAvliI HILGER,LIMITED,

' O'F LONDON, ENGLAND.

roLAnnuETnre APPARATUS.

ApplicationlerlMay 12, 1923. Serial No. 638,520.

To all whom t may concern:

Be it known that I, PERCY ROBERT ORD, a subject of the King of GreatBritain, residing at 75A, CamdenRoad, London, England, have invented newand useful Impro-vements in Polarimetric Apparatus, of which thefollowing is a specification.

In apparatus' for measuring the optical rotation, namely, the rotationof the plane f of polarization of a substance, it is customary to allowa beam of lightpolarized in a ixed and known plane by a polarizing prismknown as a polarizer to pass through a known length of the substance,as, for lnstance, a sample of liquid contained in a tube havingtransparent ends. The rotation is then measured by the examination ofthe resultant beam of light by a second polarizing prism known as theanalyzer which is mounted so as to rotate about the optical axis of theapparatus and is provided with means for measuring its rotation. Whenusing the instrument the position of the analyzer for extinction ofthelight is first ascertained, the substance is then introduced and theposition of the analyzer when extinction 'of light takes place is againascertained. The rotation of the analyzer from one position to the otheris the optical rotation of the substance.

Various devices have been used with the polarizer in order to obtainmore accurate setting, for example, the Lippich two field. system inwhich two polarizing prisms are so arranged that the field is dividedinto two portions whose planes of polarization are slightly inclined toeach other. In this oase the light is in no orientation of the analyzerwholly extinguished in both portions of the field simultaneously but theanalyzer is so adjusted that the parts of the field are made of equalintensity.

A telescope is usually provided at the eye end of the apparatus whichtelescope is focused' on a sharp line of demarcation of the two parts ofthe field so that the discrimination'of dierences of brightness is assensitive as possible.

The present invention relates to polarimetric apparatus in which thefield is di vided into at least two portions.

According to this invention ,.no' variation occurs inl the focusin .ofthe dividing line of the two parts of t 'e field as a. result ofintroducing the liquid or substance under observation, as the opticalelements vin the apparatus are so arranged that the divid- 1ng line isat the focus of the eyepiece and is not .viewed at any time through theliquid or substance under observation and in such an arrangement thepolarizer is preferably rotated and the analyzer is fixed (as far asobservation purposes are concerned) and is combined w1tl1 devices fordividing' the lield into two parts.'

This invention possesv that -the conditions of illuminationandabsorption of light by optical' elements are exactly the same in bothparts of the ield and remain the same whatever the refractive index orstate of homo neity of the liquid under observation, lan also thatdividing line between the two not viewed through the liquid or substanceunder observation so that the observation of thedividing line and thesharpness of its focus as seen in theg eyepiece are independent of the.optical qualities or physical state of the liquid. Liquids thereforewhich yare imperfectly mixed,- .Iturb'ed, uniltered or unclarified sothat they are in'a state which parts of the field iss the` advantagesdoes not permit of measurement 'by anyk known'polarizer, can beaccurately and easily measured. As 1s obvious, a line whlch could not beseen, through avturbid liquid can be' seen by the light transmittedthrough said liquid when the line is positioned adjacent lthe 'focus ofthe eyepiece.

The accompanying drawings .illustrate l pola-rimetric apparatus made inaccordance with this invention. Figure l is a plan partly in section,Figure 2 isa side elevation partly in section, Figure 3 is a transversesection on the line C D Figure 1 andv Figure 4 is a similar section onthe line E F Figure 2. Figure 5 is a longitudinal section of thea-nalyzer'and eyepiece and Figures 6 and 7 z' anda loayvpower positieeyepiece-j, all the elemetsmnaniefbeing mounted .in'f a casing c. Thecondensing lens b, filter c and Nicol prismd areso mountedthat they canbe rotated. The Nicol prisms L are so constructed and mounted that theirplanes of polarizationn make any desired angle between each other, andthe equally inclined plates z' are so arranged in relation to the ,ofvpolarization of the 'two' Nicol prisms are 'rellectors can be rotatedineitherdirection thus allowing ojf the adjustment of the zero position ofa scale m which' is'provided with verniers In. TheY scale is on thesideof the circle as shown and can be Vconveniently read through'twomagnifying glasses o. p

scale. i Figs. 6 and YV7 show the Nicol prisms in two differentpositions. These prisms as usual, give twoY parallel rays and the'twoinclined platesl refract these .rays so as to bring t em together. Toset the scale at 'zero' the screw Z is rotated until the two halvesoifltheeld are of :equal intensity,

there being no liquid in the container. Ad-

justnient'is' theneffected, the two prism VI1, making equal angles withthe plane of polarization of the polarizer.

In using .the Ainstrument the Nicol prism' el formingthe polarizer isrotated but the Nicol prisms la, forming the analyzer are stationary,thev advantage gained by such an arrangement being that .the dividingedge or edges of the parts of the eldof view retain their positionunchanged as seen yby the observer.

or reflecting light onjto thel waan-aasl flgLI lpolai-n'ietric"apparat,Ya; polarizer, an analyzer, a containerv for the sub- ]ect-underobservation located betweenthe .polarizeif ,and the ana yzer, saidanalyzer including means for dividing the field of view into two parts.

2. In polarimetric apparatus, a polarizer, anYY analyze-r, a containerfor the subject under observation located between the p'olarl.

- lieldof view into two parts, anda container forthe subject underobservation located between the analyzer and the rotatable mount. v s.4. In polarimetric apparatus, a condensing lens, a filter and a Nic-olprism -secured toa rotatablemount, an analyzer comprising two Nicolprisms arranged to 4divide the lield of view into two parts, a container'for' thelsubject under observation located between the analyzer and therotatable mount, and an eyepiece soarranged that its focus'is at thedividing line' Iof the two 'parts of the field of view. Y

5. -In polarimetric apparatus, a polarizer, an analyzer a container forthe subject under observation located between the polarizer and theanalyzer, said analyzer includingV two Nicol prisms and n two inclinedplates for dividing the field ofYV view into two, parts. v

In testimony that I claim the foregoing as my invention I have signed myname this third day-of May, 1923.

PERCY YROBERT om).V

